CITY Comptroller Alan Hevesi received more than $40,000 in campaign contributions from contractors building a water tunnel for the city while his office was auditing the project, The Post has learned.

Records show the three main contractors behind the Department of Environmental Protection’s water-tunnel project opened up their pockets to Hevesi’s war chest just two months after his audit began, giving him 22 donations totaling $42,850 from Nov. 7, 1998 to Dec. 21, 2000.

Hevesi on Monday released an audit of Water Tunnel No. 3, saying the project was moving too slowly and that larger contracts should be awarded to complete the aqueduct by 2008.

Executives and employees of Grow Tunneling Corp. in Manhattan funneled $25,350 to Hevesi, while $8,000 came to the comptroller from workers of Perini Corp. in Westchester, another tunnel builder.

A third construction company, Skanska JV in Queens, provided $5,000 in contributions to Hevesi, while the owners of the Ferrara Brothers Co., which provides concrete for the tunnel, ponied up $4,500.

Hevesi’s report focused primarily on the timetable of the construction of the aqueduct, but took the companies to task for not drilling at a rapid enough pace.

Hevesi’s audit also criticized the muck-removal system employed by the contractors, saying its slow conveyor belt impeded progress in building the tunnel in Queens.

Hevesi spokeswoman Cathie Levine said there was no connection between the donations to the comptroller’s mayoral campaign and the audit.

“We keep a fire wall between the comptroller’s office and the campaign,” Levine said.

“We don’t know whether a contributor is involved in the audit because the comptroller’s office doesn’t know who gives to the campaign.”

Hevesi’s campaign strategist – Hank Morris – said it was not improper or unethical to accept the donations.

“We comply with Mark Green and Peter Vallone’s campaign-finance law,” said Morris, referring to the public advocate and City Council speaker who are running against Hevesi for mayor.

More than $1.4 billion has been spent on building the 31-year-old tunnel that will allow the city to take its two other water tunnels off-line for repairs.

Hevesi’s audit estimated the full project may cost nearly $6 billion and not be finished until 2020. The aqueduct’s contractors also contributed to some of Hevesi’s opponents, giving $5,500 to Vallone and $5,250 to Bronx Borough President Fernando Ferrer.